...a lot of speculation!
For anyone interested in the color morphs of rainbow boas, you mightfind this article very interesting.
http://findarticles.com/p/articles/mi_qa3793/is_200304/ai_n9166785
It's very enlightening, I think. It's not about rainbow boas, or
even snakes, but I think it explains one thing that at least
one person (me) was confused about. In a nutshell, it explains that there are two types of melanin, black and brown, and, depending on the amount of each that is present, many different shades of colors can result. It also touches on erythrin (orange pigment).
With the info in that article combined with visual observations of BRB anery's and albinos, normal BRB's, as well as other RB subspecies, which are darker, it seems likely that rainbow boas actually don't have much erythrin (red pigment) at all, and what erythrin they have is isolated to specific spots (mainly the dorsal spots/patterns.) Much of the overall coloration is due to the amount and balance of the black and brown melanins.
This would explain several things:
1) Why the adult albino BRB has hardly any orange coloration and juvenile albinos have more orange coloration than adult albinos. (Obviously, there are not enough data points if looked at in isolation.)
2) Why adult "anery" BRB's are not that starkly different than normals (ie, brown vs orange) In other species like Kenyan sand boas, anery specimens are obviously different than normals. (ie, black and white vs. black and orange.) So it's probably likely other species might use a different pigment (erythrin, which is metabolised and not synthesized by the snake itself) for some/much of their orange coloration. I think it's also likely that juvenile BRB's start out able to produce more erythrin, then as the get older produce less of it along with greater production of melanin. Again, this would explain the BRB anery, and might also explain why juveniles of other RB subspecies are more orange as juveniles than as adults.
Speculative conclusions:
- Very little erythrin exists in the "background" (for lack of a better term) color of BRB's. This color is produced by the brown and black melanins, and can vary depending on the mix of them.
- The color of the dorsal pattern can (and normally does) have erythrin.
- There are separate genes controlling colors on different parts of the snake (ie, dorsal patterns, side spots, "background color", etc.)
I find this stuff very interesting, because if I'm even in the right ballpark, it is a wonder of evolution. I would think all these combinations of pattern and/or color mutation give rainbow boas the ability to evolve and adapt quite nicely and efficiently.
Any thoughts/criticisms? Anyone still awake? 
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Thanks,
Ed
